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Re: Review Comments for draft-nottingham-http-link-header-05

From: Sean B. Palmer <sean@miscoranda.com>
Date: Fri, 17 Apr 2009 19:18:13 +0000
Message-ID: <b6bb4d890904171217t567def42r2196c0a730b6afdd@mail.gmail.com>
To: Julian Reschke <julian.reschke@gmx.de>
Cc: HTTP Working Group <ietf-http-wg@w3.org>, www-archive <www-archive@w3.org>
On Fri, Apr 17, 2009 at 7:43 PM, Julian Reschke wrote:

> A TAG finding is not a standard.

Well, who decides how much standing a TAG finding, or a W3C
recommendation, or an IETF RFC, or an ISO standard has?

But even socially speaking, there is some obvious substance here: the
TAG finding was announced by Roy Fielding, an author of the HTTP RFC.
And the TAG chair is another author of the HTTP RFC.

This isn't just somebody's opinion on a mailing list, it's a W3C
resolution of something that had been causing intense argument for
years and years.

> And even if it was, not stating anything about retrieval
> wouldn't conflict with it.

Well it makes the Web Linking specification inconsistent. If you can
use extension relations as RDF properties, then the only way you can
tell whether they're valid is to dereference them. And Web Linking
says you SHOULD NOT dereference them... so why force people to do it?

You can be compatible with RDF, or you can be incompatible. But at the
moment it's being quasi-compatible, which isn't good.

> (I'm honestly trying to understand the implications!).

The most concise way that I can put it is this:

If Link is supposed to be compatible with RDF, then you have to
explain why you're not mandating 303 responses for extension
relations. If Link is not supposed to be compatible with RDF, then you
have to let RDF people know so that they won't be misled.

> Extensibility is already there for Atom relations

It'd be interesting to survey how often Atom IRI relations are used in
proportion to Atom registered relations.

> and as far as I recall, the TAG likes URI-based extensibility

But they haven't resolved uriMediaType-9 yet... :-)

> Reversed domain names would be a new approach to do distributed
> extensibility. If this would be used, people will build bridges between
> the new system and URI based extensibility anyway.

Possibly, but possibly not? The HTML WG link types registry makes it
look like people care about extensibility. But, to be cynical, perhaps
they really care about politics and transparency and so on?

Those are good things to care about, but it's not Web Linking's place
to try to fix that. The point should be to judge how often people are
really going to want to implement extensions. How can we gauge how
popular it will be?

> I believe that distributed extensibility based on URIs is good.

Where do you use it, incidentally?

> If the semantic web community is so convinced about it, why isn't
> there a W3C Recommendation which clearly states how to deal with
> RDF predicates that happen to be identified by an HTTP URI?

I'd guess because the RDF Core WG was disbanded before the TAG
resolution was made, and because it tends to be covered in notes such
as the following:

Best Practice Recipes for Publishing RDF Vocabularies

Cool URIs for the Semantic Web

Again I'm not defending this design, and my proposal is to eschew the
thing entirely. But if you're going to encourage compatibility with
RDF, it's got to be done right if Web Linking to be a decent

Sean B. Palmer, http://inamidst.com/sbp/
Received on Friday, 17 April 2009 21:04:31 UTC

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